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1932 Carl D Anderson discovers the positron, the antimatter counterpart to the electron, for which he would be awarded the 1936 Nobel Prize

1939 Albert Einstein and Leó Szilárd write to US President Franklin D Roosevelt warning of Nazi attempts to develop a nuclear weapon and urging that the American government initiate a project to create one of their own

1820 Birth of John Tyndall, known for his many contributions to experimental physics, including showing that the Earth’s atmosphere causes a greenhouse effect

1835 Birth of Elisha Gray, the inventor of the music synthesiser and an inventor who held more than 70 patents -– although he lost out to Alexander Graham Bell on that for the telephone